Fluid-operated tool



July 31, 1928. 1,678,734

w. KUHN FLUID OPERATED TOOL Filed March 16, 1927 "wt/y TOR Ln-mm mi/mATTORNEY Patented July 31, 1928. 1

UNITED STATES WILHELM KI THN, F FRANKFORT-dN-THE-MAIN, GERMANY.

FLUID-OPERATED TOOL.

Application filed March 10, 1927, Serial No.

The invention relates to an improved method of and means for operatingthe distributing valves of pressure fluid, more particularly pressureair operated tools having a reciprocating piston or striking member.

In tools of this kind one of the principal aims is to'make thedistributing member,

usually a sliding sleeve valve, as simple of construction and as lightas possible. Heavy 19 slide valves must have large operative surfacesfor the pressure air serving toactuate them, and are very liable to wearand tear in consequence of the heavy impacts which arise, whichliability is accentuated by the usually complicated forms of the valves.

The construction of the distributing valve may be considerablysimplified if the pressure required for reversing the valve is obtainedby intermittently stopping a flow of pressure air passing in contactwith the distributing valve. This method has, however. so far not beenextensively used owing to the fact that it involved a very highadditional consumption of pressure air which outweighed the advantagesobtained.

One object of the present invention is to minimize to a very largeextent the loss of pressure air incidental to this method of operatingthe distributing valve, so as to avoid the main drawback of this method,whilst retaining all the advantages which may be attained in otherdirections by the use of said method. ,To this end and according to theinvention, the reversal of the distributing valve at the end of theworking stroke of the tool, is initiated or started by stopping theoutflow of pressure air from a conduit associated with the valve surfaceto be acted upon, such stopping being effected by the striking member orreciprocating piston of the tool at the required time. The reversemovement of the distributing valve is then completed by an additionaland 'direct admission to the same surface of the distributing valve ofpressure air passing to the other side of the piston.

Another feature of the invention is the provision of a separatebalancing conduit or passage which connects the casing of thedistributing valve with the main cylinder of 174,346, and in GermanyFebruary 25, 1925.

the tool in. such a manner that one port of the balancing conduit orpassage is covered and uncovered by the distributing slide valve, Whilstthe other port of the said conduit or passage is adapted to be uncoveredby the piston or striking'member of the tool on its return strokeearlier than the port of the previously referred to conduit associatedwith the distributing slide valve.

A further improvement according to the invention consists inconstructing the distributing slide valve as a sleeve valve in such amanner that the valve controls a conduit leading to the front space ofthe cylinder,

which conduit serves both as a pressure air admission and exhaustconduit, by means of a single annular flange, and thatpressure airpasses to the cylinder on. one side of said an nular flange during thereturn stroke of the piston, whilst exhaust air passes from the cylinderinto the atmosphere on the other side of the said annular flange duringthe working stroke of the piston, so that the slide valve is heldsecurely in both end positions by the pressure of the pressure air orthe exhaust air respectively.

The accompanying drawings show by way of example a preferredconstruction embodying the features of the invention.

Fig. 1 shows a pneumatic hammer with the distributing valve in theposition occupied during the working stroke.

Fig. 2 shows the said hammer with the distributing valve in the positionoccupied during the reverse stroke. 85

Referring to the drawings, A designates the cylinder of the pneumatictool and B is the piston which is adapted to move to and fro in thecylinder. The piston B is adapted to strike against a tool D, such as asnap set, chipper, slotting tool or the like. 0 designates a cylindercover screwed upon or otherwise connected to the cylinder A, said coverbeing providedwith an admission conduit 10 for the pressure air. 11designates an annular space which communicates with the admissionconduit 10 and also communicates through radial passages l and throughthe distributing sleeve valve S with the space above or behind thepiston 13'. The

distributing sleeve valve S is adapted to slide up and down in thecylinder A, and is formed with an annular portion of an internaldiameter corresponding to the external diameter of the piston B, anupper annular portion of larger diameter, and an annular flungehaving anupper end surface 12, a lower end surface 13 and a peripheral surface 19which is the QperativevalVesur the flange 15, to a port 1 l opening intothe cylinder. 6 is a passage leading from the annular space 11 to thelowest point of the annular space7. Sis a passage arranged above thepassage 6 also leading from the annular space 11 to the annular space 7.16 is a balancing passage or conduit having aport 17 opening into thecylinder, such port being arranged below the port 14, and a port 18opening into the annular space? As ma Y be seen fromFi 1 the assa e. 6communicates with the passage 5 in the lower position of thedistributing valve S, only through a very narrow annular space lyingbelow the surface 13 of the flange 15 so that pressure air passing fromthe passage 6 into the passage 5, is throttled.

During the workingstroke, see Fig. 1, pressure air passes from theconduit 10, through the annular space 11, passages 1 and the sleevevalve S, into the space behind the piston B and drives the piston in thedirection of the arrow towards the tool D. At the same time pressure airpasses from the annular-space 11, through the small passage 6 and thenarrow annular passage under the surface 13 of the valve S to thepassage 5, and through the latter passage into the space in front of thepiston B by the lateral port 14. The flow of the air into the passage 5,14 is throttled to a very considerable extent owing to the small area ofthe aassageti' and the annular space under the slide valve, andconsequently only a small amount of pressure :air passesthroughthe-conduit 5, 1 1 into the cylinder. This air, together with the erahaust air which is being driven out bysthe piston 13 'duringthe workingstroke, is dis charged through passage 2, the annular space 3, past theend surface 12 of the slide valve into the exhaust passage iand thenceinto the atmosphere. The end surface 13 .of the slide valve is thereforeduring the working stroke of the tool not subjected to. the highpressure of the pressure air, as said piston. 7 charged into t-lieopenthrough the passages pressure air is throttled whilstflowing past thesurface 13 into the conduit 5.

As soon as the piston B covers the port 14: of the passage 5 during theworking stroke, the outflow of the pressure air from the passage5 intothe cylinder ceases and consequently the pressure in the passage 5 andin the annular space below the surface 13 increases. By thisincrease-ofthe pressure, the

reverse movement of the slide valve is initiated or started. After ashort movement of the slide valve from the position shown in Fig. 1towards the position shown in 2, the passage 8 is uncovered by theannular .flange 15, and at the same time or very shortly afterwards theconduit 2 is also placed into communication with the annular space,7,see Fig. 2, so that a full flow of pressure air will take place past thesurface 13. of the distributing valve and into the conduit. 2, andthence into the space in front of the piston B, whereby the'piston B isreturned.

It will thus be seen that the reverse movcment of the slide valve w hichhas been initiated by pressure air admitted through the passage 6 assoon as the port 14: was closed by the piston B,-is completed bypressure air admitted through passage 8 which pressure air also servesfor returning the piston 13. The surface 13 of the distributing 'valveremains during the whole return movement of the pistonB loaded by thepressure air, and consequently the slide valve is held safely in'it-supper position of Fig. 2. In the upper position ofthe slide valve S, theair supply passages 1 serving for the working stroke, are closed, whilstthe passage Qlead inginto: the exhaustp assage 4 is open.

As soon as the piston B during its return strokeuncovers the port 1d ofpassage 5, the passage 5 perfo-rmsthe same function as the passage 2,that-is, it admits pressure air in front of the piston B serving toreturn the The-air behind the piston isdis- 1 and 9. r V p At the end ofthe return stroke the piston enters the slide valve Sand at the same.time closes the exhaust passage 9. The airwhich remainsbehind thepiston, is thus enclosed between the piston and the cover C inknown-mannerand is compressed. This compressed .air cushion exerts pressureon the annular surface. a-? of theslide valve and forces the slidevalveback into the position shown in Fig. .1. During this movement ofthe valve, the passage 8 is closed by the flange 15 so that during thefollowing working stroke only a small quantityof pressure air flowsthrough the narrow passage 6 past the surface 13 into the passage 5. Itmay be pointed out that during the: working stroke, ex.-

haust air passes past the surface- 12 of the slide valve into thepassage4, the slide valve being firmly held in the lower position shownin Fig. 1 by the pressure of the live air acting on the surface a-c, asalso by the pressure of the exhaust air from the front of the cylinder.

In order to reduce as far as possible the amount of pressure air passingduring the working stroke through the passages 6, 5, 14 into the spacein front of the piston B and yet effect the reversal of the slide valveat the correct time, the pressure air admitted through the passage 6must be strongly throttled and the port 14; of the conduit 5 must becovered by the piston B at the earliest possible moment. In consequenceof this, in the case of short stroke pneumatic hammers, the port 14 hasto be arranged so high up that it is nolonger uncovered by the front endof the piston B during the return stroke, before the piston has effectedthe necessary compression, so that the surface 13 of the slide valve isnot relieved from pressure at the right time, that is, before thereversal from the position shown in Fig. 2 into that shown in Fig. 1takes place.

In order to meet this difliculty a balancing conduit 16 may be providedin the case of short stroke tools, which conduit terminates at one endin a port 17 opening into the front cylinder space and at the other endin a port 18 opening into the annular space 7, the arrangement beingsuch that the port 18 remains covered during the working stroke of thevalve, but is uncovered during the return stroke of the piston beforethe compression above the piston commences. The conduit 16 thereforerelieves the pressure upon the surface 13 against the pressure existentin the front of the cylinder in time, that is, before the slide valve ismoved down.

During the working stroke the piston then first closes the port 14: ofthe conduit 5 so that pressure air is prevented from flowing out of theconduitfi and by the increase of its pressure is enabled to start theupward reversal of the slide valve. Before the reversal of thevalve-commences, the port 17 is also covered by the piston B so that theconduit 16 is inoperative during said reversal at the end of the Workingstroke. Before the piston 13 on its return stroke (see Fig. 2) passesthe port 9, the port 17 of the balancing conduit 16 is uncovered by thepiston so that on the reverse movement of the valve caused by thecompression between the piston B and the cover O, pressure air flowingbehind the surface 13 can freely pass into the front cylinder space byway of the conduit 16, so that the balancing of the pressure on thesurface 13 takes place. In the end position of the slide valve shown inFig. 1, the flange 15 shuts off the port 18 of the release conduit 16 sothat when the pressure in the passage 5 commences to increase, thepressure on the surface 13 will not be prematurely released before theclosing ofthe port 17, I

I claim: r

1. In a pressure-air operated tool the combination of: a cylinder, apiston working in said cylinder, means for supplying pressure air tosaid cylinder, means for discharging air from said cylinder, adistributing valve in said cylinder having both of its ends stepped andbeing adapted at the upper end to control the supply of air from saidpressure air supplying means to the upper end of the cylinder for theworking stroke and at the lower end to control the discharge of airthrough said discharging means from the upper end of the cylinder, aconduit associated with the valve which is open to the pressure airsupply and to the cylinder during a part of the working stroke of thepiston and is adapted to be closed by the piston before the end of theworking stroke for the purpose of increasing the pressure in saidconduit and thereby starting the reverse movement of the valve, a secondconduit adapted to be rendered operative by the valve shortly after thereverse movement of the valve has started,'for completing the reversemovement of the valve, said second conduit communicating at one end withthe pressure air supply and at the other end with the front end of thecylinder, and a third conduit likewise adapted to be rendered operativeby the valve shortly after the reverse movement of the valve hasstarted, for the purpose of allowing of the passage of additionalpressure air past the lower end of the valve into the cylinder, saidthird conduit communicating at one end with the lower end of the valveand at the other end with the front end of the cylinder, substantiallyas described.

2. A fluid operated tool having a casing, a piston adapted toreciprocate in said cas ing, means for admitting pressure fluid to saidcasing, means for discharging pressure fluid from said casing, a slidevalve controlling the admission and discharge of the pressure fluid, andpressure fluid operated means for operating said slide valve, said meanscomprising a conduit associated with the slide valve which is open tothe pressureair supply and to the cylinder during a part of the workingstroke of the piston and is adapted'to be closed by the piston beforethe end of the working stroke for the purpose of increasing the pressurein said conduit and thereby starting the reverse movement of the valve,and a second conduit adapted to bcome operative shortly after thereverse movement of the valve has started, for completing the reversemovement of the valve, said second conduit communicating at one end withthe pressure air supplyand at the other end with the front end of thecylinder, substantially as described.

3. A fluid operated tool comprising, a cylinder, a piston adapted toreciprocate in said cylinder, means for admitting pressure air to anddischarging exhaust air from the said cylinder, a slide valvecontrolling the distribution of the pressure air and the exhaust,

pressure air operated means for operating the reverse movement of thevalve at the end of the working stroke, and means for passing anadditional flow of-pressure air past the same surface of the valve intothe front end of the cylinder, said latter means being controlled by theslide valve and becoming operative immediately after the reversemovement has commenced, and means for admitting pressure air to thefront end of the cylinder controlled by said slide valve, said meansbecoming operative just before the completion of the said reversemovement of the valve, substantially as described.

4:. A pressure-air operated tool, comprising in combination a cylinder,a. piston adapted to reciprocate in said cylinder, means for supplyingpressure air to said cylinder, meansfor discharging air from saidcylinder, a slide valve for controlling the supply and discharge of theair, means for operating said slide valve, said means comprising anannular flange on said slide valve having a peripheral operative surfaceand an annular operative flat surface, means for supplying a throttledpressure air flow to said annular surface when the slide valve is in theposition corresponding to the working stroke of the piston, a conduitleading in said position of said valve from said annular surface to apoint in the front part of the cylinder, means on said piston forcovering the end of said conduit leading into the cylinder for thepurpose of increasing the pressure upon the annular surface, whenstarting the reverse movement of the valve,

and a balancing conduit leading from the peripheral surface of saidflange to a point between the frontend of the cylinder and the end ofthe first mentioned conduit, said balancing conduit serving to balancethe pressure upon the saidannular surface at the end of the returnstroke of the piston against the pressure existent in the front of thecylinder, substantially as described.

5. In a pressure-air operated tool the combination of: a cylinder, apiston working in said cylinder, a distributing sleeve valve in saidcylinder having a single annular flange, a peripheral valve surface onsaid annular flange, a first annular end surface on said annular flange,a second annular end surface on said annular flange, means formaintaining a throttled pressure air flow past the said first annularend surface and into the front part of the cylinder, means on the pistonfor intermittently closing said air flow and increasing the pressure ofsaid air upon said first annular end surface to start the reversemovement of the valve at the end of the working'stroke of the piston,means for passing a further flow of pressure air past the said firstannular end surface of the said annular valve flangeand into the frontend of the cylinder, said means being controlled by said peripheralvalve surface of the said annular flange, and means for passing exhaustair from the front end of the cylinder past the second annular end faceof said annular flange, whereby the said valve is held securely in bothend positions, namely by the air pressure of the live air flowing intothe front of the cylinder acting on the first annular end surface of theflangein the upper position corresponding to the return stroke of thepiston and by the pressureof the live air acting on the upper surface ofthe valve,

as also by the pressure of the exhaust air from the front of thecylinder acting on the second annularend surface in the lower positioncorresponding to the working stroke of the piston.

' 6. In a pressure-air operated tool the combination of: a cylinder, apiston working in said cylinder, a distributing sleeve valve in saidcylinder having a single annular flange, a peripheral valve surface onsaid annular flange, a first annular end surface on said annular flange,a second annular end surface on said annular flange, means formaintaining a throttled 'pressure air flow past the said first annularend surfaceand into the front part-of the cylinder, means on the pistonfor intermittently closing said air flow and increasing the pressure ofsaid air upon said first annular end surface to start the reversemovement of the valve at the end of the Working stroke of :the piston,

means for passing a further .flow of presface of said annular flange,whereby the said valve is held securely in both'endpositions, namely bythe air pressure of the live air flowing into the front of the cylinderacting on the first annular end surface of the flange inthe upperposition corresponding to the return stroke of the piston and saidperipheral flange surface for relieving by the pressure of the live airacting on the the pressure on the first annular end surface 1 uppersurface of the valve, as also by the before the reversal of the valveinto the pressure of the exhaust air from the front positioncorresponding to the Working 5 of the cylinder acting on the secondannustroke of the piston.

lar end surface in the lower position corre- In testimony whereof I havesigned my spending to the Working stroke of the pisname to thisspecification. ton, and a balancing passage controlled by WILHELM KUHN.

